Research

Current projects

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CooperationWhy do we seem generous by default?

According to both standard economic and evolutionary theory, a rational individual should look out for his own best interests. But, does looking out for your own interests mean that you are necessarily selfish? Why is it that people often make sacrifices to help strangers they know they’ll never see again and who will never be able to reciprocate? Why is it that in laboratory games—where an individual can choose to cooperate or to take advantage of an anonymous stranger—people often generously pay? Using computer simulations, we have shown that organisms evolve to be generous to avoid the potential costs of mistaking a repeated interaction and a one-time interaction (see here). Why might our default expectation be that those we encounter we might re-encounter? Using additional simulations of the ancestral ecology, we have shown that a chance encounter with a random individual in fact predicts an increased probability of a future encounter with that same individual (see here).This is one of many plausible selection pressures that would cause our psychology to suspect that those we meet we will meet again, and to bet on it by being generous by default.

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CharityWhat do we really care about?

Charities differ widely in their efficiency--the amount of good done for every dollar spent. Yet, donors show little propensity to “shop around” despite the efforts of charity-evaluating organizations such as GiveWell. As some charities are a hundred times more efficient than others in addressing the same issues, the social benefit of understanding and shifting giving behavior cannot be overstated. Using experimental methods, combined with theories generated by evolutionary psychology and evolutionary dynamics, we address the following questions: What are the ultimate motivations for charitable giving? Under what conditions are people more likely to seek efficiency information when deciding where to give? What are low-cost ways to make these conditions more prevalent? We believe exploring individuals’ ultimate reasons for giving is capable of furnishing deep insights, better-articulated predictions, and––if correct––inexpensive viable solutions. This work is in collaboration with Dr. Martin Nowak (Program for Evolutionary Dynamics). Professor Krasnow and Professor Nowak received a Mind Brain & Behavior grant to study the motivational basis of charitable giving in 2014.

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PunishmentOur psychology inserts the self into third-party punishment

Humans sometimes intervene in conflicts among third parties. In the lab, this is studied using the third-party punishment game, where a third party (person C) has the chance to pay money to punish an individual (person A) who has treated another (person B) poorly. Even under anonymous conditions designed to remove any reputational concerns for the punisher (person C), punishers nonetheless sometimes punish bad actors. Why should this be the case? We propose a simple explanation: the mind of the punisher views the behavior of person A as self-relevant. Our evolved psychology reasonably expects that if someone treats another person poorly, there is an increased likelihood that the person would also treat you (and your kin and allies) poorly. Thus, punishing an individual who treats another person poorly may actually be in your best interest. We have found that third-party punishers assume that poor treatment of others indeed indicates that they will also be treated poorly, and that third-party punishers' estimates of how they would be treated by A predicts how much they punish A on behalf of B. This evidence is consistent with the view that our punitive psychology evolved to defend personal interests within ancestral human environments. In other work, we are exploring how this deterrence psychology can explain other puzzles including: punitive behavior in situations of inequality, the evolution of cooperation in even large groups, and different motivations to punish bad behavior within and across group boundaries.

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Adaptations in Spatial Cognition for GatheringWomen excel and calories count

In this line of research, we focus on the collection of mechanisms that enables learning the location and characteristics of gatherable items (such as food and tools), remembering these details, and later using them for efficient navigation back to these items. Using Japanese and American samples, we have found that although men tend to score more highly on general spatial navigation tasks, women are able to more accurately remember the location of gatherable plant sources. Additionally, both men and women demonstrate more accurate navigational memory for higher caloric density foods, such as avocados, than lower calorie foods, like celery. These findings were observed even when controlling individual differences in general spatial ability, experience with the particular environment, liking of the food items, etc. Our results suggest that the human mind appears equipped with a navigational gathering adaptation that encodes the location of gatherable foods in spatial memory, and that this mechanism seems to be more generally activated in women who ancestrally foraged more often than men.

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Music, genes, and cultural universals What are the adaptive functions of music?

In two separate projects, we aim to examine music from an evolutionary perspective. In the first, we are testing the music perception abilities, receptivity to music, and musical behaviors of individuals with imprinting disorders as well as typically developing children and adults. Genomic imprinting refers to variation in the expression of a gene depending on the sex of the parent from whom the gene is inherited. When both the madumnal (maternally derived) and padumnal (paternally derived) genes are present, we see typical development. However, there are disorders in humans that are caused by the expression of only the madumnal OR padumnal gene (i.e.,Prader-Willi Syndrome and Angelman Syndrome). This provides a unique opportunity to examine what would happen when the madumnal or padumnal genetic component is unopposed. Our project investigates whether music is implicated in the divergent interests of madumnal and padumnal genes, informing theories of its evolution and core functions. In the Natural History of Song project, we use methods from cultural anthropology, musicology, and evolutionary psychology to address two fundamental questions about music’s most basic form, human song: What, if any, are the universal functions of music? Are there cross-cultural, structural similarities to music, and do they vary systematically across different domains of song? Answers to these questions will not only uncover cross-cultural patterns of human behavior, but will also enable the evaluation of hypotheses concerning the adaptive significance of music in human societies.